i know what you mean, we relinquish control of our lives and completely place it at the mercy of our doctors to do whatever however they fit. it takes a lot of courage to do that.
Those thoughts, what if our doctor is wrong? what if its too much? thats just our minds are trying to look out for ourselves.

Besides trusting our doctors, I think the only thing we can trust is our own body. If something is bad for you, you will feel it, if something is good, you will feel that too.